Voter polls on John McCain and Barack Obama are all over the map: Gallup has them neck-and-neck, while LA Times/Bloomberg and Newsweek say Obama leads by up to 15 points. What gives? One expert says the latter polls relied too heavily on Democrats. "We know that the best predictor of how someone is going to vote is their party ID," Pew Research editor Richard Morin tells CQPolitics.
If the pro-Obama polls balance out Dems and Republicans, he says, Obama's lead shrinks to single digits or even disappears. But Morin stresses that the pollsters didn't do it on purpose. “Embedded in the operations of polling are subtle differences that result in skews—and they can be either Republican skews or Democratic skews.”